Identification and localization of surface sialylated glycoconjugates in Actinobacillus pleuropneumoniae by direct enzyme-colloidal gold cytochemistry.
Electron microscopic examination of ultrathin sections of 5 strains of Actinobacillus pleuropneumoniae stained for polysaccharides with ruthenium red revealed considerable variability in the amounts of preserved capsular material among the 5 serotypes studied. The amount of capsule was inversely related to the extent of outer membrane-associated sialylated glycoconjugate as evidenced by the degree of binding by colloidal gold-labelled neuraminidase at the cell surface. Serotypes 1, 3, and 5 possessed a well-developed and continuous capsular layer. In serotypes 2 and 7, the capsule consisted of a broken patchy layer that left much of the underlying outer membrane exposed. Morphometric analyses of the mean frequencies of neuraminidase-conjugated gold particles over the perimeters of the A. pleuropneumoniae cells showed that the lowest mean frequencies were observed in serotypes 1, 3, and 5, whereas the second highest and highest mean frequencies were observed in serotypes 7 and 2, respectively. Evidence suggested a serotypic difference in the amount of capsule present and this correlated inversely with the number of sialylated glycoconjugates, which appear to be localized in the outer membranes of the A. pleuropneumoniae cells.
Steffens
W L
WL
Department of Anatomy and Radiology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Byrd
W
W
Kadis
S
S
D000188:Actinobacillus / Q000032:analysis* / Q000648:ultrastructure; D000818:Animals; D006001:Glycoconjugates / Q000032:analysis*; D006046:Gold; D006651:Histocytochemistry; D008854:Microscopy, Electron; D009439:Neuraminidase; D011135:Polysaccharides, Bacterial / Q000032:analysis
D006001:Glycoconjugates; D011135:Polysaccharides, Bacterial; D006046:Gold; D009439:Neuraminidase